GB2033588A

GB2033588A - Apparatus for checking the cage of a constant velocity joi

Info

Publication number: GB2033588A
Application number: GB7932694A
Authority: GB
Original assignee: Finike Italiana Marposs SpA
Current assignee: Finike Italiana Marposs SpA
Priority date: 1978-09-25
Filing date: 1979-09-20
Publication date: 1980-05-21
Also published as: DE2938662C2; JPH0156699B2; GB2033588B; ES484674A1; FR2436970A1; DE2938662A1; US4364181A; JPS5598330A; IT1108236B; FR2436970B1; IT7803539A0

Description

1 GB 2 033 588 A 1

SPECIFICATION

An apparatus for checking the cage of a constant velocity joint The present invention relates to an apparatus for checking the cage of a constant velocity joint, said cage 5 incl uding an outer wal 1 with openi rigs for housi rig the joi nt ba 1 Is.

One of the most used types of constant velocity joints for front-wheel drive motor vehicles is comprised of an outer main member, or bell member, having a splined shaft meshing with the wheel hub; an inner member, called second main ball member, coupled to the drive shaft of one of the front wheels of the vehicle; an intermediate member, called ball cage; and six balls housed in relevant openings of the cage and 10 cooperating with the bell member and the second main ball member.

The operation of this type of joint is well-known and is not described herein except, in part, for the cage.

Function of the cage is to hold the six balls, permitting the transmission of the rotary movement from the second to the first main member and thus to the wheel.

With reference to Figures 1 and 2, the cage 1 comprises an outer wall 2 having an inner surface 3 and an 15 outer surface 4, constituted by portions of theoretically concentric spherical surfaces, and two plane base surfaces 5, 6, having the shape of circular crowns.

The outer wails of cage 1 has six openings 7,8,9,10,11,12 which serve, as previously mentioned, to house the joint balls.

In order that a correct and lasting working may be obtained, the different elements of the joints must have 20 rather narrow constructional tolerances and therefore it is important to check, after machining, their main dimensions and geometrical characteristics.

With regard to the cage, the Applicant deems that in view of its shape and particular functions, checkings, for example of diameters and coplanarity, carried out in conventional ways are not sufficient.

Thus, object of the invention is to provide an apparatus having features particularly suited for this type of 25 piece, so that the piece may be checked in a novel and really effective manner.

A secondary object is to provide an apparatus capable of checking the cage in a single checking station, with short checking time and relatively low constructional costs.

These and other objects and advantages are attained by an apparatus for checking the cage of a constant velocity joint, said cage including an outer wall with openings for housing the joint balls, the apparatus comprising, according to the invention, checking means with checking elements adapted to cooperate with points of the periphery of the openings; and processing means connected to the checking means, the processing means including first and second processing circuits, the first processing circuits being adapted to process signals provided by the checking means for providing signals responsive to the positions of the central points of the openings, the second processing circuits being connected to the first processing circuits 35 for defining a reference geometric plane, and for providing measurement signals responsive to the distances of said central points from the reference geometric plane, for checking the coplanarity of the central points.

The apparatus permits to cheek the height of the openings and the coplanarity of the centres of the openings. The checking of coplanarity is carried out assuming that the central points, or centres, of the openings lie on determined generatrices of the same cylindrical surface. The geometric plane nearest, on the 40 average, to the centres of the openings is detected, preferably by the method of least squares and the distances of the centres of the openings from this plane are measured.

According to anotherfeature of the invention, said checking means comprise further checking elements for cooperating with points of the cage outerwall along diametral directions and the processing means comprise third processing circuits forobtaining further measurement signals responsive to the diametral 45 dimensions of the outer wall of the cage and to the position of the centre or centres of the outer wall, the second processing circuits being connected to the third processing circuits for defining the reference geometric plane depending, too, on the position of the centre or centres of the outer wall, and for providing the relevant measurement signals depending on the differences among the distances, from the reference plane, of the centres of the openings and of at least one of the centres of the outer wall.

An arrangement according to the invention will now be described in more detail by way of example and with reference to the accompanying drawings, in which:

Figure 1 and Figure 2, already mentioned and described, are, respectively, a vertical section and a horizontal section of the cage of a constant velocity joint; Figure 3 is a simplified vertical section of an apparatus for checking the cage of Figures 1 and 2, according 55 to the preferred embodiment of the invention; Figure 4 is a plan diagram of the arrangement of the contacts of the apparatus of Figure 3 which carry out checks, along diametral directions, on the inner surface and the outer surface of the cage; Figure 5 is a simplified vertical section of the apparatus of Figures 3 and 4, along a plane passing through the central points of two opposed openings of the cage, perpendicularly to the base surfaces of the cage; 60 Figure 6 is a partial plan view of the apparatus of Figures 3 to 5, showing the arrangement of the measuring heads which check the cage openings; and Figure 7 is a block diagram of the detecting and processing circuits of the apparatus of Figures 3 to 6.

With reference to Figure 3, the cage 1 to be checked is maintained in measuring position by a thrusting device 13, vertically movable, which thrusts the cage through springs, not shown, towards three rests, one of 65 2 GB 2 033 588 A which, 14, is shown in the figure. Mechanical references, not shown, guarantee the suitable angular positioning of the cage, cooperating, preferably, with the periphery of one or more openings. Thrusting device 13 can be lifted by an amount sufficient to permit the loading and unloading of the cage.

In the meridian plane of cage 1 corresponding to the plane of Figure 3 there are arranged eight contacts 15-22. Contact 15 is rigidly coupled to an arm 23 movable about a fulcrum 24. Arm 23, in its turn, carries a measuring head 25, of---cartridge"type, having a contact 26 in touch with a reference surface of a member 27.

To member 27 is fixed another measuring head 28 having its contact 29 in touch with an arm 30 movable about a fulcrum 31. Contact 16 isf ixed to arm 30. Contact 17 is in touch with a point of the equatorial plane of the outer surface of the cage diametrically opposite to the point touched by contact 15. Contact 18 touches a10 point of the outer surface of the cage diametrically opposite to the point touched by contact 16; the two contacts 16,18 are respectively symmetrically arranged above and below the equatorial plane of cage 1. Contact 18 is fixed to an arm 32 movable about a fulcrum 33.

The position of arm 32 is detected by a measuring head 34 having its contact 35 in touch with a fixed reference surface 36.

Contact 19 is rigidly fixed to an arm 37 which is supported by a parallelogram type set including two flexible laminae 38,39. A stationary member 40 carries a plate 41 supporting two ends of laminae 38,39 and a pin 42 about which is pivotable a transmission lever 43. At one end of lever 43 is rotatably mounted a roller 44, which can cooperate with a reference surface of an element 45 fixed to arm 37. Lever 43 has at its other end a reference element 46 cooperating with a reference surface 47.

The position of arm 37 is detected by a measuring head 48 fixed to a stationary support 49. Contact 20 is in touch with a point of the inner surface of the cage diametrically opposite to the point touched by contact 19; the two contacts 19,20 are symmetrically arranged, respectively below and above the equatorial plane of cage 1. Contacts 21, 22 touch two diametrically opposite points of the inner surface of the cage, which lie in the equatorial plane of the cage.

Contact 21 is fixed to an arm 50 movable about a fulcrum 51. The position of arm 50 is detected by a measuring head 52 fixed to a support 53 coupled to the frame of the apparatus.

The apparatus further includes (Figure 4) two contacts 54, 55 in touch with points of the outer equatorial circumference of the cage which lie in a vertical plane forming an angle of 600 with the plane of Figure 3, and two contacts 56, 57 in touch with points of the outer equatorial circumference of the cage which lie in a 30 vertical plane forming an angle of 600 with the plane passing through contacts 54, 55. Two contacts 58, 59 are in touch with points of the inner equatorial circumference of the cage which lie in the same plane passing through contacts 54, 55 and two contacts 60, 61 are in touch with points of the inner equatorial circumference of the cage lying on the same plane passing through contacts 56, 57.

Movable arms, transmission levers and measuring heads, not shown, are also associated to contacts 35 17,20,22,54-61 for detecting the position of the relevant contacts. Two shells 62, 63 fixed to frame 64 protect the contacts and the associated elements described above.

For permitting the loading and unloading of cages 1 there is provided a retraction device for contemporaneously retracting all the contacts of Figures 3 and 4 from the measuring position. This device includes a shaft 65 suitably guided vertically and a tapered truncated element 66 acting, through rollers 67, 40 68, pistons 69, 70, reference elements and transmission levers, on the arms carrying the contacts. Thus, for example, roller 68, when it is displaced towards the outside, makes lever 43 rotate counterclockwise, through reference surface 47 contacting reference element 46. Consequently reference element 71 fixed to lever 43, acting on reference element 72 fixed to arm 32, makes the latter rotate clockwise retracting contact 18 from the outer surface of the cage, while arm 37, thrusted by roller 44, retracts contact 19 from the inner surface of 45 the cage.

With reference to Figures 5 and 6, the apparatus comprises six pairs of measuring heads for checking the cage openings. One pair of heads 73,74 is shown in Figure 1. Heads 73,74, which comprise relevant movable arms 75,76 with contacts 77,78, are fixed to a plate 79 fixed to an arm 80 (Figure 6).

Arm 80 is supported by a fulcrum 81 constituted by two perpendicular laminae. Arm 80 can be made to 50 rotate about fulcrum 81 by a control device including a belt 82 and a pulley 83.

Similar support and control devices are foreseen forthe other heads, of which are partially shown only movable arms 84,85,86,87,88.

To permit the loading and unloading of the cages 1, the six pairs of heads are contemporaneously displaced by belt 82 in such a way as to move the movable arms to the positions shown, for arms 75,84-88, 55 by dashed lines ("retraction" positions).

All the measuring heads described with reference to Figures 3 to 6 are connected to a detecting, processing and monitoring unit 89 (Figure 3).

With reference to Figure 7, the operation of the apparatus will be now described.

Before loading a cage the measuring heads are moved to the retraction position actuating shaft 65 and belt 60 82. After loading the cage, the heads are moved to the measuring position and the following checks are carried out.

By summing through circuit 90 of unit 89 the signals provided bythe pair of heads having the contacts 21,22; 58,59; 60,61 three diameters of the inner surface of the cage are measured; a fourth diameter of the cage inner surface is measured summing the signals of the heads comprising contacts 19,20. In a circuit 91 65 i 4 1 3 GB 2 033 588 A 3 the signals of the pairs of heads comprising contacts 15,17,54-57 are summed so as to measure three diameters of the cage outer surface; a fourth diameter of this surface is measured by summing the signals of the heads comprising contacts 16,18.

As a matter of fact, since the measuring heads are constituted by comparator gauges, the measured 5 quantities are the deviations of the diameters from their nominal values.

By calculating through a circuit 92 of unit 99 half of the difference of the two signals of the pairs of heads having the contacts 21,22; 58,59; 60,61 three distinct checkings of the positions of the centre of the cage inner surface are carried out. Similarly, by calculating through a circuit 93 of unit 89, half of the difference of the two signals of the pairs of heads having contacts 15,17; 54,55; 56,57 three distinct checkings of the position of the centre of the cage outer.surface are carried out.

By calculating, through a circuit 94 of unit 89, the difference of the signals obtained in this way, it is possible to carry outthee checkings of the concentricity between the outer and inner surfaces of the cage, along the straight lines passing through contacts 15,17,21,22; 54,55,58, 59; 56,57,60,61. The maximum of the three valves obtained in this way can be assumed, with good approximation, as measurement of the concentrity error of the two surfaces in the equatorial plane. Itis also possible, by processing the signals of 15 only the heads described with reference to Figure 3, to check the concentricity of the two surfaces in the direction of the cage axis.

The heights of openings 7-12 or, more exactly, the deviations from the nominal height are measured by summing through a circuit 95 of unit 89 the two signals of each of the six pairs of heads described with reference to Figures 5 and 6.

By calculating half of the difference of the same signals in a circuit 96 of unit 89, indications are obtained about the height of the centres of the openings or, more exactly, the deviations in vertical direction from the nominal positions of the centres.

The most complex cheek carried out by the apparatus is that relating to the coplanarity of the centres of the openings and/or the coplanarity of the same centres and of one or both the centres of the cage inner and 25 outer surfaces.

In particular, the most significant check, relating to the coplanarity of the centres of the openings and of the centre of the outer surface, is carried out on the basis of the following arguments and processing.

The reference geometric plane which is nearest, on the average, to the seven centres is determined.

The reference plane is determined by utilizing the known method of least squares (see, for example the 30 book "Statistical treatment of experimental data" by Hugh D. Young, Mc Graw-Hill Book Company, Inc., 1962 Library of Congress Catalog Card Number 62-16764, pages 101 to 132), which is now summarized with regard to the particular application.

It is assumed that in a Cartesian space (x,y,z), in correspondence of N pairs of coordinates xi, yi (i = 1 N) the ordinates zi are known; moreover it is assumed to have a function z = f (x,y) of known form, of which it is 35 desired to determine some parameters which characterize the function in such a way that it approximates in the best way the given points (xi, yi, zi).

The best approximation is obtained in the condition in which is minimized the sum of the squares of the N distances in z direction di = f (xi, Vi) zi of the known points (xi, yi, zi) from those of the curve defined by the function.

Therefore it is necessary to minimize the sum:

N N 1i (di)' = 1i If (xi, yi) - zil 1 1 Indicating with Ai, with j = 1 k, the parameters to be determined, the condition which must be satisfied for said sum to be a minimum is that all the partial derivatives be equal to zero:

N a 1i If (xil 1 = 0 a Aj for j = 1 - k, Therefore it is necessary to solve a system of k equations with k unknowns, which can be written as follows:

N a If (xi,Yi) - zil 60 0 In the application relating to the present invention it is assumed that the contacts of the measuring heads 65 described with reference to Figures Sand 6 are zero set with reference to the theoretic equatorial plane of the 65 4 GB 2 033 588 A cage (plane z = 0 in a system of coordinates x,y,z). Moreover it is assumed that the six centres of the openings lie on generatrices of the same cylindrical surface having axis z and radius R and that these generatrices lie on three planes passing through the axis z, each plane being angularly spaced at 60'with regard to the preceding plane. The value R corresponds to the distance of the contacts of the heads of 5 Figures 5 and 6 from the axis z and is known. The function to be obtained corresponds to the above mentioned reference pl.ane. Therefore it is: f (x, y) = ax + by + c i = 1 7 j = 1 3 Al=a A2=b A3=C xi = R cos -&i (i = 1 - 6) yi = R sin iai (i=1 -6) ft, = 0,!a2 = W1 1a3 = 120', 1% = 180', 240', 6 = 230' By solving the system (1) the values of the unknowns a,b,e are found:

1 7 1 7 a = 3 R li Zi COS Ci b = 3 R 2:i zi sin -ai 1 1 1 7 - C = 7 2i Zi 20 1 After having obtained in this way, through processing carried out by a group 97 of unit 87, the unknowns a,b,c and having thus determined the reference plane, the same group 97 calculates the axial distances (along the z axis) of the centres of the openings from the reference plane:

di = zi - (axi + byi + c) i = 1 6 Then group 97 calculates the differences di - d7, namely:

Di = Zi - Z7 - axi - byi - c i = 1 6 These distances Di are assumed to be indicative of the coplanarity error of the centres of the openings and of the centre of the cage outer surface and are visualized, together with the results of the processing carried out by circuits 90,91,92,93,94,95,96, on a monitoring group 98.

The execution in the described way of the coplanarity cheek of the centres of the openings (and of one or both the centres of the cage outer and inner surfaces) is particularly important and advantageous. The check could be made in a simpler way, for example with reference to base surface 5 or 6. In this case, however, the checks would be scarcely significant because it is possible that, in a cage having openings and outer and inner surfaces exactly machined and capable to guarantee a perfect working, the plane passing through the 40 centres of the openings and of the inner and outer surfaces is not parallel to the plane, or planes, of the base surfaces.

It is evident that the described apparatus can be equipped with loading, unloading and sorting devices in orderto obtain an operation more or less automated.

It is also evident that t lle arrangement of the contacts can be modified and that the apparatus can comprise 45 a plurality of checking stations, instead of a single station.

Claims

1. Apparatus for checking the cage of a constant velocity joint, said cage including an outer wall with 50 openings for housing the joint balls, characterized in that it comprises checking means with checking elements adapted to cooperate with points of the periphery of the openings; and processing means connected to the checking means, the processing means including first and second processing circuits, the first processing circuits being adapted to process signals provided by the checking means for providing signals responsive to the positions of the central points of the openings, the second processing circuits being connected to the first processing circuits for defining a reference geometric plane, and for providing measurement signals responsive to the distances of said central points from the reference geometric plane, for checking the coplanarity of the central points.

2. Apparatus according to claim 1, characterized in that said checking means comprise further checking elements for cooperating with points of the cage outer wall along diametral directions and the processing 60 means comprise third processing circuits connected to the further checking elements for obtaining measurement signals responsive to the position of at least one centre of said outer wall, said second processing circuits being connected to the third processing circuits for defining the reference geometric plane depending on the position of the centres of the openings and on the position of the outer wall centre, the second processing circuits being adapted to provide signals responsive to the differences of the 65 4, GB 2 033 588 A 5 distances of said central points and the distance of said outer wall centre from the reference plane.

3. Apparatus according to claim 2, characterized in that said outer wall centre is the centre of the cage outer surface.

4. Apparatus according to anyone of claims 1 to 3, characterized in that said second processing circuits 5 comprise circuits for defining said reference plane by the method of least squares.

5. Apparatus according to anyone of claims 1 to 4, characterized in that said checking elements adapted to co-operate with points of the periphery of the openings comprise a plurality of measuring devices with at least two contacts for each opening, said processing means comprising fourth processing circuits for obtaining signals responsive to the heights of the openings.

6. Apparatus according to claim 2, characterized in that the further checking elements comprise 10 measuring devices adapted to detect at least six dimensions of the cage outer surface, along diametral directions.

7. Apparatus according to claim 2, characterized in that the further checking elements comprise measuring devices adapted to detect at least six dimensions of the cage inner surface, along diametral directions.

8. Apparatus according to claims 6 and 7, characterized in that said processing means comprise fifth processing circuits for providing signals responsive to the possible concentricity errors of the cage inner and outer surfaces.

9. Apparatus according to claim 1, characterized in that it comprises an arrangement for simultaneously retracting all the measuring sensors that co-operate with the points on the periphery of the openings.

10. Apparatus according to claims 6 and 7, characterized in that it comprises a device for contemporaneously retracting all the measuring devices adapted to detect dimensions of the cage inner and outer surfaces.

11. Apparatus according to claims 6 and 7, characterized in that said processing means comprise sixth processing circuits for checking three diameters of the inner surface and three diameters of the outer surface 25 in an equatorial plane of the cage, along three directions forming angles of 6T.

12. Apparatus according to claims 6 and 7, characterized in that the further checking elements comprise two measuring devices for detecting a diametral dimension of the cage inner surface, in a plane inclined with respect to the equatorial plane, and two measuring devices for detecting a diametral dimension of the cage outer surface in another plane inclined with respect to the equatorial plane.

13. Apparatus for checking the cage of a constant velocity joint, substantially as described with reference to Figures 3 to 7 of the accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon Surrey, 1980. Published by the Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.